How can I create dynamic brick/tile-like geometry?
The Wall Factory is a step in the right direction, and it's already included in blender.

To activate, go to User Preferences (Ctrl + Alt + U). Then go to the Add-ons tab and enable Add Mesh: Extra Objects.

To add a new wall, press Shift + A and then go to Mesh > Extras > Wall Factory





However, it doesn't look like I can go back and modify things like brick size or grout width after I've created the wall.